Aqueous coating systems based on physically drying urethane acrylates

Abstract

The invention relates to radiation curable coating systems on the basis of aqueous polyurethane dispersions, to a method for the production thereof, to the use of the coating systems as paints and/or adhesives, and to objects and substrates provided with said paints and/or adhesives.

The invention claimed is: 
     
       1. A radiation-curable aqueous dispersion based on polyurethane acrylates consisting of as builder components
 A) one or more compounds of monohydroxy-functional alcohols comprising (meth)acrylate groups, 
 B) polyester polyols obtained from components consisting of
 B1) 1,2-Ethanediol, 1,2-propanediol, 1,3-propanediol, neopentyl glycol, trimethylolpropane, glycerol and/or castor oil, and 
 B2) phthalic acid, phthalic anhydride, isophthalic acid and/or terephthalic acid, 
 
 C) optionally monomeric mono-, di- and/or triols in each case having a molecular weight of from 32 to 240 g/mol, 
 D) one or more compounds having at least one group which is reactive towards isocyanate, and additionally having groups which are nonionic, ionic or capable of the formation of ionic groups, which have a dispersing action for the polyurethane dispersion, 
 E) organic polyisocyanates, and 
 F) optionally mono- and diamines and/or mono- or difunctional amino alcohols compounds, 
 
       and optionally reactive diluents comprising at least one group which can undergo free radical polymerization. 
     
     
       2. The radiation-curable aqueous dispersion based on polyurethane acrylates according to  claim 1 , wherein the polyester polyols B) are present in an amount of from 5 to 75 wt. %, and wherein components A to F add up to 100 wt. %. 
     
     
       3. The radiation-curable aqueous dispersion based on polyurethane acrylates according to  claim 1 , wherein the polyester polyols B) have an OH number of 20-500 mg of KOH/g of substance. 
     
     
       4. The radiation-curable aqueous dispersion based on polyurethane acrylates according to  claim 1 , wherein the one or more compounds of monohydroxy-functional alcohols comprising (meth)acrylate groups A) comprise 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, pentaerythritol triacrylate, dipentaerythritol pentaacrylate, the addition product of ethylmethylheptanoic acid glycidyl ester with (meth)acrylic acid and/or technical grade mixtures thereof. 
     
     
       5. The radiation-curable aqueous dispersion based on polyurethane acrylates according to  claim 1 , wherein B1) is 1,2-ethanediol, 1,2-propanediol, neopentyl glycol or trimethylolpropane; and wherein B2) is isophthalic acid or terephthalic acid. 
     
     
       6. The radiation-curable aqueous dispersion based on polyurethane acrylates according to  claim 1 , wherein the one or more compounds D) comprise 2-(2-amino-ethylamino)ethanesulfonic acid, 3-(cyclohexylamino)propane-1-sulfonic acid, the addition product of isophoronediamine and acrylic acid, hydroxypivalic acid, dimethylolpropionic acid, triethanolamine, tripropanolamine, N-methyldiethanolamine, N,N-dimethylethanolamine, monofunctional mixed polyalkylene oxide polyethers which contain ≧40 mol % of ethylene oxide units and ≦60 mol % of propylene oxide units, or mixtures thereof. 
     
     
       7. The radiation-curable aqueous dispersion based on polyurethane acrylates according to  claim 1 , wherein the organic polyisocyanates E) comprise 1,6-hexamethylene-diisocyanate, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (isophorone-diisocyanate or IPDI), 4,4′-diisocyanato-dicyclohexylmethane, homologues or oligomers of 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (isophorone-diisocyanate or IPDI) or 4,4′-diisocyanatomethylcyclohexane with biuret, carbodiimide, isocyanurate, allophanate, iminooxadiazinedione and/or uretdione groups, or mixtures thereof. 
     
     
       8. A process for the preparation of the radiation-curable aqueous dispersions based on polyurethane acrylates according to  claim 1 , comprising
 a. reacting components A-D with component E in one or more reaction steps wherein, optionally, a neutralizing agent is added before, during or after the preparation of the prepolymer to produce the ionic groups necessary for the dispersing operation, 
 b. dispersing the product of the reaction by adding water to the prepolymer or transferring the prepolymer into an aqueous reservoir, wherein, optionally, component F is added before, during or after the dispersing. 
 
     
     
       9. The process for the preparation of the radiation-curable aqueous dispersions based on polyurethane acrylates according to  claim 8 , wherein the molar ratios of isocyanate groups in (E) to groups in (A), (B), (C) and (D) which are reactive towards isocyanates are from 0.8:1 to 2.5:1. 
     
     
       10. The process according to  claim 8 , further comprising admixing one or more reactive diluents with at least one group which can undergo free radical polymerization. 
     
     
       11. A coating, lacquer or adhesive obtained from the radiation-curable aqueous dispersion according to  claim 1 . 
     
     
       12. A coating composition comprising the radiation-curable aqueous dispersions based on polyurethane acrylate according to  claim 1 , and crosslinking agents based on amino resins, blocked polyisocyanates, non-blocked polyisocyanates, polyaziridines and/or polycarbodiimides, and/or one or more further dispersions. 
     
     
       13. A substrate coated with coating composition according to  claim 12 . 
     
     
       14. The radiation-curable aqueous dispersion based on polyurethane acrylates according to  claim 1 , wherein C) is present.